Cabrera, who signed with the Royals in December, is batting .479 this spring with five doubles, two homers and 16 RBIs and 17 runs scored.
Cabrera hit a two-run homer in Thursday's 9-8 win over the Mariners.
The Royals received contradictory reports when they were contemplating signing the free agent outfielder, who was released by Atlanta on Oct. 19 soon after they were eliminated from the National League playoffs.
Cabrera hit .238 in August and .246 in September. He finished with a .255 average, four home runs, only 34 extra-base hits and 42 RBIs in 147 games.
"You get some conflicting reports on what he had left," Royals manager Ned Yost said. "We felt real strong he had a lot left and he's proven that."
The 26-year-old Cabrera will be the starting center fielder for Kansas City on opening day. He said he played at 220 pounds last year, but reported to spring training 20 pounds lighter.
"Sometimes a change of scenery is huge for a guy," Yost said. "Melky had some really good years with the (New York) Yankees. He came off not a very good year last year and that happens. Every once in a while a guy will have a bad year.
"I think Melky kind of refined what he wanted to do as a player and refocused and rededicated himself as a player. He got in great shape, was very serious about his winter workouts."
While Cabrera made $3.1 million last year, he signed a one-year contract with the Royals for $1.25 million.
"I always thought he was a great player," Royals pitcher Bruce Chen said. "I've seen him with the Yankees and he was very, very good. I can't believe we got him. We got him so cheap because last year was a down year for him. But he's looking really good."
Cabrera was interested more in an opportunity to play every day than in trying to get a bigger contract.
"A lot of times signing a guy revolves around how much money can I get?" Yost said. "Well, Melky's concern was, I just want to come back and prove I can play again. That was a main factor for me was that he was serious about bouncing back. Money was secondary compared to prove to baseball that he's the player he once was and what everybody thinks he can be.
"It's a serious part in my thinking. This guy can help us. He's looking petty darn good. He's really swinging the bat really well for us right now."
Yost said he talked to Joe Torre, who managed Cabrera in New York, about him in spring training.
"Joe just loved him, really loved his talent and thought he was a great kid," Yost said.
Royals hitting coach Kevin Seitzer loves Cabrera's swing.
"It's very low maintenance, fundamentally sound, very quick hands, a very explosive swing compared to what I saw on video," Seitzer said. "A lot of it comes back to his approach at the plate, what he's trying to do. We hit it off immediately in the cage. I got high expectations for this kid this year."